Gas operated firearms are efficient but require frequent maintenance. Build ups of debris such as vaporized metals, carbon, and other impurities on the bolt, particularly the bolt tail, may cause the firearm to foul if the debris is not routinely removed.
In gas impingement systems like those found in the AR-15, gas operated firearms extract spent casings and load a new cartridge in the chamber by harnessing energy from high pressure gases generated during firing. High pressure gas is siphoned off from the barrel after a fired bullet passes a gas port. Gas enters the gas port, travels down a gas tube, typically located above the barrel, and into a gas key. The gas key channels the gas into the bolt carrier. The bolt carrier houses the bolt, forming a piston powered by the high pressure gases. The high pressure gas impinges upon the bolt tail, causing the bolt and bolt carrier to move and cycle through the chambering operation.
In order to efficiently transfer the energy contained in the high pressure gas to other portions of the bolt carrier assembly, the bolt tail comprises a bolt tail top and a bolt tail body. Both portions have circular cross sections. The bolt tail top has a concave curvature, having a larger diameter at a first end which curves down to a smaller diameter at a second end where the bolt tail top connects with the cylindrical bolt tail body. In order to ensure proper functionality and reliability, debris must be removed from both portions of the bolt tail and both portions must be polished.
Several debris removal approaches exist. The usual method to clean the bolt tail is to scrape it with a sharp metal object followed by brushing with various solvents and compounds to finally clean and polish the part.
Various tools have been designed to make this task easier. A product called a “Carbon Removal Tool” manufactured by Magna-matic of Waldo, Wis. discloses an adjustable metal scraper featuring a pin which is inserted into the bolt, allowing the adjustable metal scraper to be held against the bolt tail and rotated, thereby removing debris from the bolt tail. This design is disclosed in U.S. Pat. No. 8,327,571 (the '571 patent).
Another approach is disclosed in U.S. Patent Application Publication No. 2011/0113669 (the '669 Application) wherein the bolt tail is first inserted into a channel and rotated against an adjacent scraper blade.
Known cleaning and polishing tools, including those disclosed in the '571 patent and the '669 Application, require a final action to remove the last remaining residue. For example, devices in accordance with the '669 Application accomplish the final cleaning and polishing action by having a user place a polishing pad around the bolt tail and inserting the assembly into an adjustable polishing arm guide hole. The user may press a polishing arm down on the bolt tail and rotate the bolt in order to complete the cleaning process. Additional compounds can be used to facilitate this action.
Existing bolt tail cleaning and polishing solutions are relatively large, making them difficult to carry in a cleaning kit. In fact, many existing devices are larger than the bolt itself. Additionally, existing bolt tail cleaning devices require two separate processes to clean and polish the bolt tail. The first process is used to scrape away the majority of the debris deposited on the bolt tail. The second process is required to fully clean and polish the bolt tail surface.
Given the foregoing, what is needed are devices which remove debris from the bolt tail of a firearm and polish the bolt tail in a single process. Additionally, durable devices are needed which have a small footprint, preferably smaller than a bolt, in order to facilitate carrying the bolt tail cleaner in a cleaning kit. In sum, what is needed is a is a cost effective, durable, portable device which, via a single process, removes debris and polishes the bolt tail, thereby enabling more rapid and complete cleaning of the bolt tail both in the barracks and in the field.